Organopolysiloxane composition for rendering cellulosic materials nonadherent and method of applying same



United States William S. Kather, Schenectady, Alexander A. Litster, Cohoes, and Edgar D. Brown, In, Schenectady, N. Y., assignors to General Electric Company, a corporation of New York No Drawing. Apphcation March 15, 1954, Serial No. 416,422

Claims. (Cl. 260-291) This invention is concerned with rendering cellulosic materials non-adherent to various organic solids. More particularly, the invention is concerned with compositions capable of rendering paper or paperboard non-adherent to normally adherent materials such as, for instance, asphalt, unvulcanized rubbers, and other high molecular weight organic polymers, said composition of matter comprising an organopolysiloxane fluid and small amounts of an aluminum compound selected from the class consisting of aluminum hydroxide and aluminum silicate. The invention also embodies methods for rendering the above mentioned paper or paperboard nonadherent.

Cellulosic fibers in the form of cellulosic papers and paperboard are used extensively as confining and shipping means for various highly adhesive materials including such organic compositions as asphalt or pitch, tar, various unvulcanized rubbers, particularly synthetic rubbers, and other high molecular weight organic polymers. For optimum use of these cellulosic containers, it is essential that they be capable of being readily separated or stripped from the cargo contained therein. Thus, in the transportation and shipment of asphalt used for roofing purposes, the asphalt is generally poured while still hot into a container, such as a carton, bag or drum whose sides are cellulosic in nature. After cooling, the asphalt becomes quite hard and can be readily transported with little difficulty. At its destination of use, it is essential that this paper in whatever form be readily stripped from the asphalt so as to permit easy access to the latter without any extraneous portions of the paper or fibers thereof adhering to the asphalt so as to undesirably affect the constitution of the asphalt.

Various treatments have been accorded :these types of papers which are often referred to as anti-blocking paper. One method for treating the paper to render it anti-blocking comprises treating the paper in a three-coat operation with (l) finely divided clay and casein, (2) finely divided clay, and (3) polyvinyl acetate. $uch paper provides release by fracture of the clay coating, but the polyvinyl acetate remains on the adhesive material. Another method commonly employed in the art involves applying several thicknesses of polyethylene to the paper, usually by treating the latter with solutions of the polyethylene. A still further method for treating cellulosic materials to render it impermeable, particularly to asphalt and to permit it to be readily removed from direct contact with the latter, involves depositing a double coating on the cellulosic material, the first coating being of clay and the second coating being of methyl cellulose and starch.

However, all the foregoing methods have been exceedingly expensive and in many respects have not been too satisfactory since too often it has been found that these adhesive materials,particularly asphalt, which ap-. parently has a high affinity for eellulosic fibers, stick to atent O "ice the anti-blocking paper so that great difiiculty is encountered in attempting to separate the latter from the asphalt.

U. S. Patent 2,588,367 describes the use of methyl hydrogen polysiloxanes in combination with water-soluble cellulose ethers for the purpose of treating anti-blocking paper to render it less adherent to ordinarily adhesive organic compositions. Although such combinations of ingredients are ordinarily helpful in reducing the ad hesive properties of the paper, nevertheless much is left to be desired from such treatment of the paper. Often, the release properties are unreliable and the release characteristics are not uniform throughout the surface of the paper. In addition, it is essential that, in order to obtain optimum release properties, the treated paper be aged for extended periods of time, c. g., by storage before it is useful for release purposes; this is necessary because accelerated aging by high-temperature treatment is not usually available commercially in paper-treating establishments. Furthermore, paper such as parchment paper cannot be heated above C. without deleteriously affecting the paper. Moreover, the fact that the methyl hydrogen polysiloxane employed in preparing treating mixtures for the cellulosic paper, in addition to being unstable and hazardous, is in short supply, unduly limits the amount of treating materials which can be em ployed for anti-blocking purposes.

Unexpectedly, we have discovered that a mixture of ingredients comprising a fluid, non-resinous organopolysiloxane containing a minor proportion of either aluminum hydroxide or aluminum silicate, when employed as the essential treating ingredients for cellulosic products, markedly reduces the adhesion of the latter to the various adherent materials referred to above, and these release characteristics or anti-blocking properties of the treated paper are constant enabling one to use the same treated paper several times at least without undesirable diminution in the anti-sticking properties of the paper. In accordance with a preferred form of the instant invention, cellulosic sheet material is treated with an emulsion comprising a non-resinous, fluid organop-olysiloxane containing a minor proportion of an aluminum compound selected from the class consisting of aluminum hydroxide and aluminum silicate. For optimum anti-blocking characteristics, metallic salts are also advantageously used in the treating mixture.

The organopolysiloxanes employed in the practice of the present invention are those which are fluid and stable (resistant to increase in viscosity) at normal temperatures (of 25 to 30 C.) and which do not need a solvent to be liquid at such temperatures. This requires that the organopolysiloxane be non-resinous since: the usual organopolysiloxane resins are solids or relatively unstable in the absence of a solvent.

Among the organopolysiloxanes which may be employed in this invention are those having the general formula where R is a monovalent hydrocarbon radical, preferably a monovalent lower alkyl radical (e. g., methyl, ethyl, propyl, etc), x has a value of from 1.0 to 1.5, y has a value from 0.75 to 1.25, and the sum of x and y has a value of from about 2.0 to 2.25, inclusive. These organohydrogen polysiloxane fluids employed in the practice of the present invention may contain traces of hydroxy radicals due to the incomplete condensation of the silicols obtained as a result of hydrolysis of the intermediate organohydrogen hydrolyzable silanes, for instance, methyldichlorosilane. These organohydrogen polysiloxane fluids may be either cyclic or linear polymers. The linear polymers may be chain-stopped with trimethylsilyl groups, or even with diorganohydrogen silyl units as, for instance, units having the formula (CH3 3Si-O-- or (CHa)2HSi-O- Examples ofsuch organohydrogen polysiloxanes may be found, e. g., in Sauer Patents 2,595,890-891, in Wilcock Patent 2,491,843, and in Barry Patent 2,590,812.

A still further class of organopolysiloxane fluids which may be advantageously employed in the instant invention comprises liquid organosiloxanes of the formula where the various Rs represent monovalent hydrocarbon radicals, and a is a whole number equal to at least 3, and in which every oxygen atom is situated between two silicon atoms, every silicon atom is attached through oxygen to at least one other silicon atom, and each terminal silicon atom in the SiOSi skeletal structure is joined to three R groups. R in the instant formula may be, for instance, alkyl (e. g., methyl, ethyl, propyl, isopropyl, butyl, etc.), aryl (e. g., phenyl, diphenyl, naphthyl, etc.), alkaryl (e. g., tolyl, xylyl, ethylphenyl, etc.), aralkyl (e. g., benzyl, phenylethyl, etc.), alkenyl (e. g., vinyl, allyl, methallyl, etc.), cycloaliphatic (e. g., cyclohexyl, cyclopentyl, cyclopentenyl, etc.) radicals. The presence of inert substituents on the organic radicals such as, for instance, halogens, for example, chlorine, bromine, etc., is not precluded. A more specific embodiment of such liquid polysiloxanes are those corresponding to the formula more particularly disclosed and claimed in Patnode Patents 2,469,888 and 2,469,890 issued May 10, 1949, and

assigned to the same assignee as the present invention.

It will, of course, be apparent to those skilled in the artthat in addition to the liquid, curable organopolysiloxanes described above, other organopolysiloxanes, or mixtures or blends of these organopolysiloxanes, fulfilling the above-mentioned requirements may be employed without departing from the scope of the invention. The use of fluid organopolysiloxanes appears to be critical, not only for optimum release properties, but also for purposes of employing these liquid organopolysiloxanes in usable form, preferably in the form of emulsions which are advantageously used as the treating medium for the release paper. For optimum results, the organopolysiloxane advantageously contains from 1.75 to 2.2 organic groups or total organic groups and hydrogen atoms per silicon atom.

An organopolysiloxane fluid which has been found to be eminently successful for release purposes when applied to paper to be used for anti-blocking purposes is one which comprises a polymerizable, fluid, intercondensed product of hydrolysis comprising a mixture of methylchlorosilanes composed essentially, by weight, of 50 to 75% dimethyldichlorosilane, 1 to trirnethylchlorosilane, 10 to 35% methyltrichlorosilane, and from about 1 to 10% of a methylchlorodisilane (or mixture of methylchlorodisilanes). The methylchlorodisilane or mixture of methylchlorodisilanes may be in the form of tetrachlorodimethyldisilane, pentachloromethyldisilane, trichlorotrimethyldisilane, dichlorotetramethyldisiiane, etc., or mixtures of these methylchlorodisilanes, either alone or with hexachlorodisilane. Generally, these methylchlorodisilanes may comprise from about 1 to as high as 12 to 15% of the mixture of methylchlorosilanes in the starting hydrolysis product. In combination with this hydrolysis product, it is essential for optimum results in the practice of the present invention to employ a metallic salt which is believed to act as a curing agent for the hydrolysis product. This metallic salt may be either a salt of an organic or inorganic acid.

The intermediate hydrolyzable mixture of methylchlorosilanes is generally obtained by passing methyl chloride over silicon in the presence of copper at ele vated temperatures in the manner disclosed and claimed in Rochow Patent 2,380,995 issued August 7, 1945 and assigned to the same assignee as the present invention. The reaction product thus obtained, in addition to containing the above-described methylchlorosilanes in the stipulated proportions, also contains small amounts of silicon tetrachloride, tetramethylsilane, hexamethyldisilane, methyl-substituted p-olysilanes (with or without silicon-bonded chloride) containing more than two silicons attached by silicon-silicon linkages, etc. These additional ingredients are present generally in insignificant amounts and may be removed if desired from the by drolyzable mixture prior to effecting conversion to the methlypolysiloxane state. The usual methods of hydrolysis with water are employed and it is generally desirable to neutralize the acidic hydrolysis product sulflciently to obtain an essentially neutral product. Thereafter, the more volatile components such as hexamethyldisiloxane and octamethylcyclotetrasiloxane are advantageously removed from the hydrolysis product to use these materials for making silicone oils or rubbers; however, these volatiles need not be removed since equivalent results are obtained even if they are allowed to remain in the methylpolysiloxane.

The metallic salts used in combination with the abovedescribed organopolysiloxanes, and in particular the above-identified hydrolysis product of the intermediate mixture of ingredients comprising methyltrichlorosilane, trimethylchlorosilane and a methylchlorodisilane or mixture of methylchlorodisilanes (for brevity this hydrolysis product will hereinafter be referred to as methylpolysiloxane), are those which by themselves are either considered as being capable of effecting cure of the organopolysilovane (e. g., those containing an average of from 1.2 to 1.9 organic groups per silicon atom) or else in the case of organopolysiloxanes which are not considered to be of the curable type (such as those having an organic-tosilicon ratio of from 2 to 2.25 organic groups per silicon atom), are capable of imparting optimum anti-sticking characteristics in the presence of the aluminum compound. The mechanism whereby these metallic salts exercise their function is not clearly understood in view of the fact that in connection with curable organopolysiloxanes (e. g., those containing an average of from about 1.2 to 1.9 organic groups per silicon atom), they are usually considered as being curing agents for the latter organopolysiloxanes, while in the case of organopolysiloxanes containing an organic-to-silicon ratio above 1.9 to as high as 2.25, the metallic salts are ordinarily incapable of exercising any significant degree of curing of the organopolysiloxane. It has been found, however, that without the metallic salt, whether used in combination with organopolysiloxanes which are considered to be either the curing or non-curing type, the optimum antiblocking properties are not attained despite the presence of the aluminum compound. It requires the concurrent presence of the aluminum compound and the metallic salt to bring out the low anti-sticking characteristics of the treated cellulosic material. 1

As a further guide for the choice of the metallic salt to be employed in the practice of the present invention, attention should be given to whether it exercises any deleterious, elfects on the paper-treating mixture or on the paper itself. These metallic salts, (for brevity they will hereinafter be referred to as metallic salts) may be eitherwater-soluble or soluble in the organopolysiloxane. Where it is desired that the material being treated should be free of any color change due to any coloring in the treating composition, the metallic salt should itself be free of extraneous color either when employed in its treating form, for instance, in emulsion or dispersion form, or when present on the treated paper.

Various classes of metallic salts satisfying therequire- .ments recited above may be employed. One class of such salts comprises metallic salts, particularly the watersoluble metallic salts whose metal ion is derived from group IV of the periodic table. Among metallic salts which may be employed are, for example, water-soluble salts (both inorganic and metalloorganic) of, for instance, titanium, zirconium, tin, lead, etc., such as zirconium tetrachloride, zirconium oxychloride, including its hydrates, zirconium sulfate and its hydrates, zirconium acetate, zirconium nitrate, zirconium ammonium carbonate, zirconium oxybromide, stannous chloride, zinc acetate, zinc nitrate, nickel sulfate, nickel acetate, nickel chloride, titanium oxychloride, titanium nitrate (TiO.N205.6I-I20), titanium oxalate, stannous gluconate (the use of this material for curing purposes of organopolysiloxanes is more particularly disclosed and claimed in the copending application of M. Michael Solomon Serial No. 416,413 filed concurrently herewith and assigned to the same assignee as the present invention), etc. Various complexes, both organic and inorganic, of these metallic salts may be employed without departing from the scope of the invention. Among such complexes may be mentioned, for instance, complexes formed by treating zirconium hydroxide with mannitol in a dilute base such as, for instance, sodium hydroxide; zirconium oxalate having the formula Zr(CzO2)2.2Zr(OH)4, etc. Also, hydrates of the various metallic salts described generically and specifically above may also be employed.

In addition to the water-soluble salts mentioned above, which are preferred, one may also employ water-insoluble metallic salts which are soluble in the organopolysiloxane and which can be readily dispersed or emulsified with the organopolysiloxane, so as to be in intimate contact with the latter in order to exercise their function. Among the metallic salts which are soluble in the organopolysiloxane are, for example, metallic salts of organic acids, for instance, acid radicals yielding the resinate, linoleate, stearate, oleate, or even the lower acid radicals such as those yielding the butyrate, octoate, hexoate, etc. radicals, as well as n-aphthenate salts. Among such metallic salts may be mentioned, e. g., lead octoate, zinc octoate, zinc naphthenate, tin naphthenate, lead naphthenate, tin ctoate, etc. The prime requisite for such types of metalloorganic salts is that they be soluble in some medium such as the organopolysiloxane or water, or be capable of being intimately dispersed or suspended so as to bring them into intimate contact with the organopolysiloxane so as to permit the metallic salt to exercise its function. The metallic salt is advantageously added just prior to application of the emulsion to the cellulosic material.

The amount of metallic salt used may be varied widely without departing from the scope of the invention. Advantageously, the metallic salt (other than the aluminum hydroxide and aluminum silicate) is employed in such an amount that there is present at least 0.1%, preferably from 0.5 to 14%, by weight, of the metal constituent, based on the weight of the organopolysiloxane. Optimum results generally are obtained when the metal ion of the metallic salt is within the weight range of from about 1 to 6%. The amount of metallic salt employed will depend upon such factors as, for instance, the particular metal salt used (including the metal ion), its effect on the emulsion, particularly the stability of the latter, the type of organopolysiloxane employed, the type of paper to which the treating composition will be applied, the solubility of the metallic salt as well as the medium in which the metallic salt will be used, the treating conditions includingtemperature and time of treatment, etc.

The aluminum compounds which have been found to be essential in the practice of the present invention for obtaining the unexpectedly outstanding release properties are those selected from the class consisting of aluminum hydroxide and aluminum silicate. Hydrates of these aluminum compounds may be employed where available and in many respects may be preferred because of their increased water solubility. Among such aluminum compounds may be mentioned aluminum hydroxide having the formula Al(OH)3, Al2(OH)s; aluminum silicate (in the pure or somewhat impure state) having the formula AlzSiOs, etc., and hydrates and complexes of these aluminum compounds. Included in the scope of the present invention is the use of aluminum compounds which are prepared in situ in the treating mixture whereby ingredients designed to form either aluminum hydroxide or aluminum silicate are incorporated in thetreating mixture, and in such mixture theseingredients interact to give either the aluminum hydroxide or the aluminum silicate. Included among such reactants may be mentioned, for example, the use of a combination of ingredients composed of an alkali-metal hydroxide (such as sodium hydroxide or potassium hydroxide) or of ammonium hydroxide with an aluminum salt such as, for instance, aluminum nitrate having the formula Al(NOa)s, or aluminum which when employed in the proper molar concentrations designed to yield the aluminum hydroxide under suitable conditions, such as neutral conditions, will give the aluminum compound, in this case aluminum hydroxide, in a form satisfactory for the practice of the present invention. Similarly, the aluminum silicate may be prepared by effecting reaction between a mixture of ingredients comprising aluminum nitrate and sodium silicate. Generally, it is preferred that the preformed aluminum hydroxide or aluminum silicate be employed in the practice of our invention in order to exercise better control on the quality and quantity of the aluminum compound employed.

The amount of the aluminum compound employed may be varied within wide limits. Amounts of the aluminum compound equal to as low as 1%, by weight, based on the weight of the organopolysiloxane have been found to exercise an improvement in the release properties. Generally, we prefer to employ the aluminum compound in amounts ranging from about 1.5% to 12% or more, by weight, based on the weight of the organopolysiloxane. Amounts of the aluminum compound in excess of 12% may be used, but care should be exercised that it does not render the aqueous emulsion unstable.

The fact that these particular aluminum compounds were so eifective in our invention was entirely unexpected and in no way could have been predicted since attempts to use other metallic hydroxides such as the hydroxides of chromium, copper, iron, nickel, and silicon, and even such materials as titanium dioxide, silica, aerogel, etc. failed to give satisfactory improvements in release properties over the same paper treated with the organopolysiloxane from which these particular hydroxides or oxides were omitted.

The treating mixtures employed in the practice of the instant invention is advantageously in the form of an aqueous emulsion or an emulsion-dispersion. The mixture of active ingredients (other than the water) in the treating mixture (this term treating mixture" will hereinafter be used to include the fluid organopolysiloxane, the metallic salt additive for the latter, the aluminum compound, aqueous medium, and any other ingredients required for obtaining stable emulsions or emulsion-dis' persions) will generally comprise from about 0.5 to 25% of the weight of the total treating mixture. I

In making such dispersions or suspensions,-various agents usually employed for thesep'urp'oses, such as dispersing or emulsifying'agents, may be used especially where the organopolysiloxane is readily emulsified in the water and where the metallic salt is water-soluble, Among such emulsifying agents may be mentioned, for instance, the sulfonated amide condensation products of fatty acids with organic amines, sulfonated aromatic and mixed alkyl aryl sulfonate derivatives, and sulfonated ster derivatives. A particularly satisfactory one is Nilo-SD which is a fatty acid amide condensate manufactured by Sandoz Chemical Works, New York, New York.

The actual amount of emulsifying or dispersing agent employed will depend, for instance, upon the type of ingredients present in the treating composition, the type of emulsifying agent'employed, the application intended, etc.- Generally, the amount of emulsifying agent satisfactorily employed may range from about 0.01 to 1%, by weight, based on the weight of the entire treating mixture. The amount used is not critical and persons skilled in the art will have little difficulty in determining readily the amount which gives optimum results. It is preferable that the emulsifying agent used be one which permits the emulsion to be stable under treating conditions but is readily broken within the interstices of the paper fibers to deposit the organopolysiloxane. Another particularly good emulsifying agent is Pluramine 5-100 (manufactured by Kearny Manufacturing Company of Kearney, New Jersey) which is also a sulfonated amide.

One method for making the treating compositions herein described and found so eminently useful for treating paper in accordance with our process comprises, first, homogenizing water with the emulsifying agent until a homogeneous suspension of the emulsifying agent and water is obtained, the latter material being generally in the form of a creamy composition. To this is slowly added the organopolysiloxane containing a small amount of an emulsion stabilizer such as, for example, oleic acid, etc. 'Ihis'mixture of ingredients is in turn again thoroughly homogenized until the organopolysiloxane is intimately dispersed throughout the water phase after which an additional amount of water is added. This material is often referred to as a master emulsion. The master emulsion is then diluted with an additional amount of water containing, for instance, the water-soluble metallic salt (assuming that such a salt is employed in this description), a colloid protector such as agar gums, casein, methyl cellulose, sodium carboxy methyl cellulose, etc. These colloid protectors may comprise from 0.1 to 0.5% of the Weight of the water added. Generally, the aluminum compound is added after the emulsion is in its ultimately diluted form.

The procedure described above for preparing water emulsions of the treating compositions herein described may, of course, be varied within wide limits and it is not intended that the description be limiting in any manner. The presence of small amounts of organic solvents, for instance, solvents for the metallic salts, etc. is not precluded, although usually this is not necessary. If any organic solvent is employed, it is preferable that one employ those which are easily volatilized at the temperature at which treatment of the paper will take place. The emulsion should be kept at a relatively cool temperature and around room temperature prior to using in order to maintain its stability. Satisfactory aqueous emulsions or dispersions may be employed which comprise, by weight, from 80-99% water, from 1-20% of the organopolysiloxane and from 0.01 to 6% or more of the aluminum compound, incorporating in the said emulsion the desired amount of the metallic salt which is required to be present in combination with the aluminum compound for bringing out optimum anti-blocking characteristics of the cellulosic material when th latter is treated with the emulsion and-subsequently dried.

Cellulosic materialswhich can be treated in accordance with our process include all types of paper, such as kraft paper, linen rag paper, rice paper, glassine, parchment, cellophane, cellulosic cloth, suliite cellulose paper, and the like; and sheeting or box materials, such as paperboard, cardboard, pulpboard, and pasteboard. If desired and practicable, treatment of the cellulosic material may be effected by adding treating compositions described above directly to the paper pulp in the beater.

The final treating mixture can be applied to the paper by any convenient means, for instance, with conventional dip or roller coating equipment, by padding, spraying, knife-coating, etc.; alternatively, the emulsion may be applied by means of a size press employed in combination with the paper machine so that the treatment of the paper is on a continuous basis taking place after the paper is formed on, for instance, a Fourdrinier machine.

The amount of organopolysiloxane which is picked up by the cellulosic material as a result of the treatment with the emulsion or emulsion-dispersion of the organopolysiloxane depends upon such factors as the absorbency of the cellulosic material, the method of application, the concentration of organopolysiloxane emulsion, etc. One of the unexpected advantages of employing the aluminum compound for the treating mixture is the fact that the organopolysiloxane pickup appears to be improved over the pickup realized employing the same treating material but omitting the aluminum compound. Generally, the amount of organopolysiloxane pickup ranges from about 0.30 to about 5% or more, based on the dry weight of the cellulosic material; the preferred pickup being within the range of about 0.5 to about 2% organopolysiloxane pickup. Obviously, larger amounts of organopolysiloxane pickup may be employed, but generally this is not neces sary and usually serves merely to increase the cost of the treatment. The'ability to obtain maximum pickup with minimum amounts of organopolysiloxane and to realize the maximum release properties is one of the unexpected and unobvious advantages of employing the aluminum compound in combination with the organopolysiloxane release material.

Following treatment of the cellulosic material with the emulsion or emulsion-dispersion, the material is advantageously dried. This drying may be carried out at room temperature (e. g., 25-30 C.) for several hours, or by passing the treated paper over heated rolls maintained at temperatures of about 50 to C. This drying step will bring out the optimum release properties of the paper without further heat treatment at the much higher temperatures required with other treatments employing organopolysiloxanes but omitting the aluminum compound. Of equal significance is the fact that these optimum release properties are immediately available without requiring aging or storage of the treated paper. Obviously, the higher the temperature, the shorter the period of exposure of the paper for removing the water and drying the paper. The time required for drying should be enough to reduce the finished paper to its normal water content which is about 3 to 7%. Times of the order of about 30 seconds to 3 minutes are usually sufficient for the purpose.

In order that those skilled in the art may better understand how the present invention may be practiced, the following examples are given by way of illustration and not by way of limitation. All parts are by weight. In all the examples, the weight percent of organopolysiloxanes, based on the weight of the cellulosicmaterial, picked up by the latter varied from about 4 to 1 /2%.

EXAMPLE 1 In this example, the organopolysiloxane employed was obtained by hydrolyzing a mixture of ingredients comprising approximately, by weight, about 5% trimethylchlorosilane, 20% methyltrichlorosilane, 70% dimethyldichlorosilane, and about 4 to 8% of a mixture of ingredients composed of chloromethyldisilanes, particularly trichlorotrimethyldisilane and tetrachlorodimethyldisilane.

This mixture of chlorosilanes was hydrolyzed with water by a continuous process which is more particularly described in Schwenker patent application Serial No. 281,716 filed April 11, 1952 and assigned to the same assignee as the present invention. The fluid methylpolysiloxane thus obtained was neutralized with solid anhydrous sodium carbonate and filtered. Thereafter this material was treated to remove most of the non-intercondensed octamethylcyclotetrasiloxane present therein, as well as low boiling materials, for instance, hexamethyldisiloxane, etc. The stripped material (that boiling essentially below 100 C.) amounted to about to of the hydrolysis product. The methylpolysiloxane fluid thus obtained was found to have a viscosity of about 90 to 100 centistokes. An emulsion was prepared composed of 50 parts of the above-obtained stripped methylpolysiloxane, parts of water, 1 part .oleic acid (as a stabilizer), and 2.5 parts of an emulsifying agent, specifically Nilo SD. This mixture of ingredients was thoroughly homogenized until a thick, creamy mixture was obtained. An additional amount o'f 27 parts water were added and the entire mixture again intimately mixed to give homogeneous master emulsion containing about 50%, by weight, of the methyl polysiloxane. To 10 parts of this master emulsion were added 87.8 parts water containing by weight, thereof of a high viscosity sodium carboxy methyl celluluose as a colloid protector. About 0.7 part of an aqueous solution of stannous gluconate containing 14% tin, by weight, was then added slowly while the mixture was being agitated. This provided a padding solution containing about 5% methylpolysiloxane in the treating mixture. Thereafter, 1.7 parts of an aqueous dispersion containing, by weight, 12% aluminum hydroxide, were added while again effecting agitation of the mixture. This treating dispersion was employed inmany of the succeeding examples for treating of various types of paper.

In the subsequent examples, where various organopolysiloxane emulsions were employed for treating cel lulosic materials, the test for determining the effectiveness of the release properties of the paper was carried out as follows. This test comprised heating an asphaltic pitch specifically G :and K roofing compound to about l85 C. and pouring it on the paper being tested to fill a ring 2.5 in diameter. After one hour when the pitch had cooled to room temperature, the paper was stripped from the pitch cylinder by exerting a force at a right angle to the plane of contact. The force was applied from a gear motor through a cord moving at a rate ofabout 4" per minute. A spring balance was employed to indicate the greatest force in grams required to obtain release of the paper from the pitch.

' EXAMPLE 2 In this example, employing the treating emulsion described in Example 1, lb. kraft paper (manufactured by Mosinee Paper Mills Company) was dipped in the emulsion and thereafter passed through squeeze rolls exerting a pressure of p. s. i. A sample of the untreated paper was also dipped in an emulsion of the above-described rnethylpoylsiloxane emulsion from which the stannous gluconate catalyst was omitted. Another sample was treated with the same emulsion as described in Example 1 with the exception that the aluminum hydroxide was omitted. The following Table I shows the results of the pitch test applied to the various treated papers. Table I describes various means whereby the paper was dried, or cured, and the conditions under which such procedures were carried out. The air-drying condition recited in Table I involved applying a temperature of about 70 to 80 C. for 2 minutes to the treated paper. The elevated temperature cure involved heating the treated paper at about 150 C. for five minutes. In addition, trimethyl end blocked methyl hydrogen polysiloxane was substituted for the met-hylpolysiloxane in. the emulsion described in Example 1, employing the same proce- 10 dure and other ingredientsdescribed in this'fexa'mple, including the aluminum hydroxide; a similar emulsion was prepared omitting the aluminum hydroxide. Kraft paper was then treated with these latter two methyl hydrogen polysiloxan'e emulsions. each of the papers prepared as described above.

Table I Pitch Test Release EXAMPLE 3 In this example, emulsions similar to that described in Example 1 were prepared with the exception that in one case the methylpolysiloxane was substituted by a methyl phenyl polysiloxane containing intercondensed dimethylsiloxy and diphenylsiloxy units in the form of a linear chain terminated by trimethylsilyl groups; and using in another instance a linear methylpolysiloxane chainstopped with trimethylsilyl groups (said linear polysiloxanes being more particularly described in the abovementioned. Patnode patents). Each of these emulsions was used to treat 35-lb. kraft paper in the same fashion as described in Example 2. The paper treated with the methyl phenyl polysiloxane emulsion was heated at 150 C. for five minutes while the paper treated with the linear methyl polysiloxan was air-dried for about 2 minutes at 70 to C. Pitch tests on each of the treated papers showed that when the aluminum hydroxide was omitted from the methyl phenyl polysiloxane emulsion, the pitch test resulted in tearing of the paper and no release thereof from the pitch surface; the presence of the aluminum hydroxide markedly reduced the adhesion of the paper to the pitch and gave a value of below 1000 grams for the pull required to separate the treated paper from the pitch ring, with no evidence of fiber adhesion. With regard to the paper treated with the linear methyl polysiloxane emulsion, the omission of the aluminum hydroxide re sulted in a pull under the pitch tests, of over 1000 grams. The incorporation of the aluminum hydroxide in the emulsion reduced this value to about 790 grams, again illustrating the improvements realizable with various organopolysiloxanes by the incorporation of the aluminum hydroxide.

EXAMPLE 4 In this example, 10 parts of the master methylpolysiloxane emulsion described in Example '1 were mixed with 81 parts water and the mixture thoroughly homogenized. To this mixture was added with stirring 0.7 part of an aqueous stannous gluconate solution (containing 14%, by weight, tin) with stirring,- this being equivalent to 2% tin based on the weight of the methylpolysiloxane. A second solution was prepared composed of 23.2 parts of a 10% sodium hydroxide aqueous solution and 40 parts water. To this solution were added approximately 16 parts aluminum nitrate [Al(N0s)3'9H2O]. This addition was carried out with stirring to give a mixture having a pH of 7. This yielded a soft fiocculent aluminum hydroxide gel which was further diluted with 22 parts of water. 8.2 parts of the latter mixture were added with stirring to the first emulsion containing the methylpolysiloxane and the entire mixture agitated until a homogeneous emulsion was obtained. This emulsion contained Table I includes test results on a 11 about 5%, by weight, thereof of the methylpolysiloxane and about 0.27% aluminum hydroxide. 35-1b. kraft paper was treated with this emulsion in the same manner as described in Example 2. The following Table II shows the formulations employed in each instance together with the drying or curing cycle applied to each treated paper. The release force in grams employing ,the pitch test is also recited in this table. Table II additionally describes results of omitting the aluminum hydroxide and of employing 4% zirconium metal, based on the weight of the methylpolysiloxane, in the form of zirconium acetate. In addition, Table II shows the evaluation of an aqueous, chain-stopped methyl hydrogen polysiloxane emulsion presently available on the market for release paper purposes, employing 4% zirconium metal and 2% tin metal, the former in the form of zirconium acetate and the latter in the form of stannous gluconate, each based on the weight of the methylpolysiloxane. Otherwise, the formulations were the same and were prepared in the same way.

Table II Organopoly- Pitch siloxane in Drying or Curing Test Treating Additive Cycle Release Mixtures Force In Grams Methylpolysi- 4% zirconium. 2 min. at 150 C 500-650 xane. D 2% tin 2 min. 7080 0.- 1500 Do 2% tin and 0.27% 2 min. at 150 C"... 75

Al(OH)3. Do Air dry 4 hrs. at 90 30 0.

Do ..do 2 min. at 7080 C... 85 Do 4% zirconium and do 75 0.27% A1(OH) Methyl hydrogen 4% zirconium... 2 mm. at 150 C 255 polysiloxane. Do 2% tin 4 hrs. at 310 130.-., 2% tin and 0.27% 2 min. at 7080 0... so

Al(OH)3.

EXAMPLE 5 This example illustrates the ability of reusing antiblocking paper prepared in accordance with the instant invention for a number of cycles. More particularly, the methylpolysiloxane treating emulsion described in Example 1 containing 0.27% aluminum hydroxide and 2% tin based on the weight of the methylpolysiloxane in the form of stannous gluconate and containing 5%, by weight, of the methylpolysiloxane, was used to treat kraft paper in the manner described above. The paper was thereafter dried for 2 minutes at about 70 to 80 C. A similar treating emulsion was prepared with the exception that the aluminum hydroxide was omitted from the treating material. Thereafter, 35-lb. kraft paper was coated and impregnated with the latter emulsion and the paper was heated for two minutes at about 150 C. Each treated paper was subjected to the pitch test described previously for determining the release force required after a number of cycles. It was found that the paper treated with the emulsion from which the aluminum hydroxide was omitted, after the first test required 650 grams force, after the second test required 1500 grams force and after the third test required 1950 grams force; the last two cycles showed unsatisfactory release due to adhesion of the paper fibers to the pitch. In contrast to these results, the paper treated with the emulsion containing the aluminum hydroxide, after the first test showed 85 grams force, after the second test 240 grams force, after the third test 350 grams'force, and after the fourth test showed 650 grams force.

EXAMPLE 6 In this example, glassine paper and parchment paper were each treated with the methyl polysiloxane emulsion described in Example 2 containing the stannous gluconate and the aluminum hydroxide, employing the same manner of treatment as described in this latter example. Thereafter the papers were dried for 2 minutes at 70 to C. The release properties of each of the samples of paper were tested by applying Scotch tape (manufactured by the Minnesota Mining and Manufacturing Company) to the various surfaces and stripped from the papers and notation made whether any fibers of paper adhered to the tape. In the case of the untreated papers, removal of the tape was either difficult or else carried with it some of the paper fibers. In contrast to this, the tape could be readily removed from the treated papers without apparent fiber adhesion.

EXAMPLE 7 In this example, a treating emulsion was prepared similarly as that described in Example 1 with the exception that the sodium carboxy methyl cellulose was omitted and, in addition, the aluminum hydroxide was replaced with varying concentrations of aluminum silicate in amounts ranging from 0.2 to 0.8 part aluminum silicate per parts of the treating emulsion. Otherwise, the emulsion including the stannous gluconate and the proportion of ingredients was the same. Thirty-five pound kraft paper was treated similarly as that described in Example 2 employing the emulsions containing the varying concentrations of aluminum silicate. These treated papers were air-dried at a temperature of about 7080 C. for 2 minutes and thereafter tested by means of the abovedescribed pitch test. The following Table III shows the release force in grams for the various papers treated with the emulsions containing the different concentrations of aluminum silicate.

It will, of course, be apparent to those skilled in the art that in addition to the organopolysiloxanes employed and described above, other organopolysiloxanes, many examples of which have been given previously, may be used without departing from the scope of the invention. In'general, the fluid organopolysiloxane is advantageously one which has a ratio of from about 1.8 to 2.2 organic groups, for instance, hydrocarbon groups per silicon atom. Preferably, at least 50% of the organic groups are lower alkyl groups, e. g., methyl groups. In addition,it will be apparent that other metallic salt agents for the organopolysiloxanes (other than the aluminum compounds), many examples of which have been given previously, may be employed in place of the stannous gluconate and the zirconium acetate recited previously. Obviously, smaller or larger concentrations of the organopolysiloxane designed to give an organopolysiloxane pickup in the cellulosic material above or below that recited in the previous examples (which ran on the order of from about to 1 /z%) may also be employed and will be found to be equally efiective.

' In addition to the sodium carboxy methyl cellulose employed in small amounts (less than 1% of the weight of the treating mixture) recited above for stabilizing the emulsion and protecting the colloid, other materials such as agar gum, casein, etc. may also be employed. The concentration of the curing agent and the aluminum hydroxide may obviously be varied within wide limits depending on the factors recited previously.

' Advantages of using the compositions herein described for the above specified purposes are manifold. By means of our invention, it is possible to obtain high quality release characteristics for highly adherent materials such as uncured synthetic rubbers, pitch, asphalt, tar, many adhesives and other type of materials. The anti-blocking properties are effective even at low concentrations of organopolysiloxane pickup; the paper treated can be given an air drying which is usually sufficient to bring out the optimum properties of the release paper without the necessity of employing high temperatures which are often impractical to use in paper making establishments.

Of equal significance is the fact that paper treated in.

accordance with our process can be employed at once for its anti-release purposes with realization of essentially optimum properties. Heretofore, organopolysiloxanes previously available on the market for the same purpose required aging, that is, storing of the treated paper for times as long as 6 Weeks, in order to bring out the optimum release characteristics of the treated paper. The re-release characteristics of cellulosic materials treated in accordance with our invention are highly attractive and up to as many as six releases have been obtained us ing pitch as a medium before any fiber adhesion of the cellulosic paper to the pitch was noted. f considerable importance is the fact that even at high temperatures, the release characteristics are maintained at optimum levels and elevated temperatures do not destroy the release film. The compositions for treating cellulosic materials herein described are readily amenable to a single step procedure and are easily regulated and controlled for adjustable organopolysiloxane pickup by minor variations in the formulations. Standard paper making or paper converting equipment is readily employed in connection with the treating operations and no precautions need be taken for any toxic materials which may be contained in the treating emulsions. In addition to imparting the highly desirable release characteristics of the paper, this treatment also imparts water repellency to the cellulosic material, especially when using zirconium salts.

Cellulosic materials treated as described above have a wide range of usefulness. Thus, asphalt or high molecular weight organic polymers, such as various synthetic rubbers, can be poured hot into containers fashioned from the treated paper or paperboard, and after cooling it will be found that solidified asphalt or polymer is readily and cleanly separated from container walls.

Our invention permits paper treated in accordance with our process to be substituted for various fabrics which have heretofore been used in contact with adhesive surfaces of electricians pressure sensitive tape, adhesive tapes used for surgical purposes, and regenerated cellulose tapes carrying a permanent adhesive upon one surface. Vulcanized or unvulcanized sheets of rubber can be prevented from adhering to each other despite the fact that these sheets of rubber are quite sticky and cohesive when in direct contact with each other. Paper treated in accordance with the instant invenion is also useful in lining various boxes of partially prebaked goods such as buns, rolls, and the like and advantage can be taken of the outstanding release properties at elevated temperatures by completing the baking cycle in the original container in which the baked goods are purchased.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. A composition of matter for rendering cellulosic fibrous sheet material non-adherent towards materials which normally adhere thereto comprising an aqueous emulsion containing a fluid organopolysiloxane, the organic groups of the organopolysiloxane being selected from the class consisting of monovalent hydrocarbon radicals and chlorinated phenyl radicals, from 1.5 to 12% by weight, of an aluminum compound selected from the class consisting of aluminum hydroxide and aluminum silicate, and a metallic salt which in combination with the aluminum compound is capable of reducing the adhering characteristics of the said sheet material treated with the said emulsion and dried, the metallic salt being selected from the class consisting of water-soluble inorganic salts, water-soluble metallo-organic salts, and organopolysiloxanewsoluble metallo-organic salts, in which the metal ion of the metallic salt is selected from the class consisting of titanium, zirconium, tin, lead, zinc, and nickel, the metallic salt being present, by weight, in an amount equal to at least 0.1%, based on the weight of the fluid organopolysiloxane.

2. A composition of matter for rendering cellulosic fibrous sheet material non-adherent towards materials which normally adhere thereto comprising an aqueous emulsion containing a fluid methylpolysiloxane, from 1.5 to 12%, by weight, of aluminum hydroxide, and a metallic salt which in combination with the aluminum hydroxide is capable of reducing the adhering characteristics of the said sheet material treated with the said emulsion and dried the metallic salt being selected from the class con sisting of water-soluble inorganic salts, water-soluble metalloorganic salts, and organopolysiloxane-soluble metallo-organic salts, in which the metal ion of the metallic salt is selected from the class consisting of titanium, zirconium, tin, lead, zinc, and nickel, the metallic salt being present, by weight, in an amount equal to at least 0.1% based on the weight of the fluid methylpolysiloxane.

3. A composition of matter for rendering cellulosic fibrous sheet material non-adherent towards materials which normally adhere thereto comprising an aqueous emulsion containing a fluid methylpolysiloxane, from 1.5 to 12%, by weight, of aluminum silicate, and a metallic salt which in combination with the aluminum silicate is capable of reducing the adhering characteristics of the said sheet material treated with the said emulsion and dried the metallic salt being selected from the class consisting of water-soluble inorganic salts, water-soluble metallo-organic salts, and organopolysiloxane-soluble metallo-organic salts, in which the metal ion of the metallic salt is selected from the class consisting of titanium, zirconium, tin, lead, zinc, and nickel, the metallic salt being present, by weight, in an amount equal to at least 0.1% based on the weight of the fluid methylpolysiloxane.

4. A composition of matter for rendering cellulosic fibrous sheet material non-adherent towards materials which normally adhere thereto comprising an aqueous emulsion containing a fluid methylpolysiloxane, from 1.5 to 12%, by weight, of aluminum hydroxide, and at least 0.1%, by Weight, based on the weight of the fluid methylpolysiloxane, of zirconium acetate.

5. A composition of matter for rendering cellulosic fibrous sheet material non-adherent towards materials which normally adhere thereto comprising an aqueous emulsion containing a fluid methylpolysiloxane, from 1.5 to 12%, by weight, of aluminum hydroxide, and at least 0.1%, by weight, based on the weight of the fluid methylpolysiloxane, of stannous gluconate.

6. A composition of matter for rendering cellulosic fibrous sheet material non-adherent towards materials which normally adhere thereto comprising an aqueous emulsion containing a fluid methylpolysiloxane, from 1.5 to 12%, by weight, of aluminum silicate, and at least 0.1%, by weight, based on the weight of the fluid methylpolysiloxane, of zirconium acetate.

7. A composition of matter for rendering cellulosic fibrous sheet material non-adherent towards materials which normally adhere thereto comprising an aqueous emulsion containing a fluid methylpolysiloxane, from 1.5 to 10%, by weight, of aluminum silicate, and at least 0.1%, by weight, based on the weight of the fluid methylpolysiloxane, of stannous gluconate.

8. An aqueous emulsion for rendering cellulosic fibrous sheet material non-adherent towards materials which normally adhere thereto comprising, by weight, (1) from to water, (2) from 1 to 20% of a fluid methylpolysiloxane, (3) from 0.01 to 6% of an aluminum compound selected from the class consisting of aluminum hydroxide and aluminum silicate, and (4) a metallic salt selected from the class consisting of water-soluble inorganic salts, water-soluble metallo-organic salts, and organopolysiloxane-soluble metallo-organic salts, in which the metal ion of the metallic salt is selected from the class consisting of titanium, zirconium, tin, lead, Zinc and nickel, the metallic salt being present, by weight, in an amount equal to at least 0.1%, based on the weight of the fluid methylpolysiloxane.

9. An aqueous emulsion for rendering cellulosic fibrous sheet material non-adherent towards materials which normally adhere thereto comprising, by weight, (1) from 80 to 90% water, (2) from 1 to 20% of a fluid methylpolysiloxane, (3) from 0.01 to 6% aluminum hydroxide and (4) at least 0.1%, by weight, based on the weight of the fluid methylpolysiloxane, of stannous gluconate.

10. The method of rendering cellulosic fibrous sheet material non-adherent to materials which normally adhere thereto which comprises treating the sheet material with an aqueous emulsion containing, by weight, (1) from 1 to 20% of a fluid organopolysiloxane, the organic groups of the organopolysiloxane being selected from the class consisting of monovalent hydrocarbon radicals and chlorinated phenyl radicals, (2) from 80 to 90% water, (3) from 0.01 to 6% of an aluminum compound selected from the class consisting of aluminum hydroxide and aluminum silicate, and (4) a metallic salt selected from the class consisting of water-soluble inorganic salts, water-soluble metallo-organic salts, and organopolysilox- .ane-soluble metallo-organic salts, in which the metal ion of the metallic salt is selected from the class consisting of titanium, zirconium, tin, lead, zinc and nickel, the

metallic salt being present, by weight, in an amount equal to at least 0.1%, based on the weight of the fluid organopolysiloxane.

l1. Cellulosic sheet material treated in accordance with the method described in claim 10.

12. The method of rendering cellulosic fibrous sheet material non-adherent to materials which normally adhere thereto, which comprises (a) treating the sheet material with an aqueous emulsion containing, by weight, 1) from 1 to 20% of a fluid methylpolysiloxane, ('2) from to water, (3) from 0.01 to6% of aluminum hydroxide, and (4) a metallic salt which in combination with the aluminum hydroxide efiects optimum-reduction of the sticking characteristics of the treated cellulosic material. The metallic salt selected from therclass consisting of water-soluble inorganic salts, water-soluble metallo-organic salts, and organopolysiloxane soluble metallo-organic salts, in which the metal ion of the metallic salt is selected from the class consisting of titanium, zirconium, tin, lead, zinc and nickel, the metallic salt being present, by weight, in an amount equal to at least 0.1% based on the weight of the fluid methylpolysiloxane and (b) drying the treated cellulosic material.

l3. Cellulosic sheet material treated in accordance with the method described in claim 12.

14. The method of rendering cellulosic fibrous sheet material non-adherent to materials which normally adhere thereto, which comprises (a) treating the sheet'material with an aqueous emulsion containing, by weight, 1) from 1 to 20% of a fluid methylpolysiloxane, (2) from 80 to 90% water, (3) from 0.01 to 6% of aluminum hydroxide, and (4) at least 0.1%, by weight, based on the weight of the fluid methylpolysiloxane, of stannous gluconate, and (b) drying the treated cellulosic material.

15 Cellulosic sheet material treated in accordance with the method described in claim 14.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A COMPOSITION OF MATTER FOR RENDERING CELLULOSIC FIBROUS SHEET MATERIAL NON-ADHERENT TOWARDS MATERIALS WHICH NORMALLY ADHERE THERETO COMPRISING AN AQUEOUS EMULSION CONTAINING A FLUID ORGANOPOLYSILOXANE, THE ORGANIC GROUPS OF THE ORGANOPOLYSILOXANE BEING SELECTED FROM THE CLASS CONSISTING OF MONOVALENT HYDROCARBON RADICALS AND CHLORINATED PHENYL RADICALS, FROM 1.5 TO 12% BY WEIGHT, OF AN ALUMINUM COMPOUND SELECTED FROM THE CLASS CONSISTING OF ALUMINUM HYDROXIDE AND ALUMINUM SILICATE, AND A METALLIC SALT WHICH IN COMBINATION WITH THE ALUMINUM COMPOUND IS CAPABLE OF REDUCING THE ADHERING CHARACTERISTICS OF THE SAID SHEET MATERIAL TREATED WITH THE SAID EMULSION AND DRIED, THE METALLIC SALT BEING SELECTED FROM THE CLASS CONSISTING OF WATER-SOLUBLE INORGANIC SALTS, WATER-SOLUBLE METALLO-ORGANIC WALTS, AND ORGANOPOLYSILOXANE-SOLUBLE METALLO-ORGANIC SALTS, IN WHICH THE METAL ION OF THE METALLIC SALT IS SELECTED FROM THE CLASS CONSISTING OF TITANIUM, ZIRCONIUM, TIN, LEAD, ZINC, AND NICKEL, THE METALLIC SALT BEING PRESENT, BY WEIGHT, IN AN AMOUNT EQUAL TO AT LEAST 0.1%, BASED ON THE WEIGHT OF THE FLUID ORGANOPOLYSILOXANE. 